using System;

​

public class Program

{

    public interface Hello

    {

        void coucou();

    }

​

    public class H

    {

        public static void Execute(ref Hello h)

        {

            h.coucou();

        }

    }

​

    public class T : Hello

    {

        public byte toto

        {

            get;

            set;

        }

​

        public void coucou()

        {

            toto += 3;

        }

    }

​

    public static void Main()

    {

        T t = new T();

        Hello hello = t;

        H.Execute(ref hello);

        H.Execute(ref hello);

​

        Console.WriteLine(t.toto);

    }

}